In today's telephony and communication networks, call completion may require traversal through multiple switches and/or network elements owned, operated or controlled by multiple service providers. Each service provider and its related network elements through which a call is routed may negatively impact the cost and quality of the call, as well as the availability of features and services.
Consider a route of a long distance communication call originated by a calling subscriber of local service provider A in one city and terminating at a called subscriber of local service provider B in another city across the country. The calling subscriber may originate the communication call using customer-premises equipment (CPE) such as a landline or wireless telephone, smart-phone, DSL modem, cable modem, computer or the like. A network element controlled by a local service provider A may receive the originating communication call.
Local service provider A may be, for example, a local telephone service provider, a wireless service provider, a cable provider, a Voice over Internet Protocol (VoIP) provider, or some other company that provides communication service to subscribers. Each different local service provider may have a different type of network element via which a CPE may send or receive calls, depending on a corresponding access technology. For instance, a local telephone company may have a local exchange switch, a cable company may have a cable modem termination system (CMTS), a wireless service company may have a cell site, base station or equivalent, a VoIP provider may use installed software on the CPE or at a local or remote server, etc.
In this example, suppose local service provider A provides plain old telephone service (POTS) to a residential land-line telephone subscriber. In order to route the originating communication call across the country to a terminating CPE using the public switched telephone network (PSTN), the communication call may be converted from the format understood by the local exchange switch of local carrier A into a telephony protocol understood by a tandem exchange A1. The originating call may then be routed through tandem exchange A1. Tandem exchange A1 may be controlled or owned by a company that may or may not be the same as local carrier A. From tandem exchange A1, the call may then be converted into another telephony protocol and routed to a long distance network element, such as a long distance switch. The long distance network element may be owned or controlled by yet another company, such as a long distance carrier. The call may be routed through potentially multiple network elements or switches in potentially multiple long distance networks controlled by one or more long distance companies. Eventually, the call may be routed to the appropriate tandem switch B1 at the called end that may be owned by yet another different company, and then to the local exchange switch controlled by local service provider B. Finally, the call may terminate at the CPE of the called subscriber.
Note that in this example, multiple carriers and multiple network elements or switches may be involved for routing the communication call—e.g., local exchange switch of local service provider A, tandem exchange A1, potentially multiple switches in one or more long distance networks, tandem exchange B1, and local exchange switch of local carrier B. At each leg of the call and sometimes even within a leg of a call, the call must be converted into a format understood by the next switch or network element. Each time a call is converted from one format into another, some data loss may occur and lead to potential call degradation. Furthermore, the overall quality of the call and the availability of feature transparency may be dictated by the lowest bandwidth transmission protocol used by one of the network elements or switches in the entire call path. For the PSTN, the lowest bandwidth protocol that all service providers are able to accommodate is typically a 64 kbps channel for the content of a circuit switched call, and a 56 kbps data stream for the signaling control of the call. If local service provider A provides a feature that requires a higher bandwidth internal to its own network, the feature may not be transparent across all networks traversed by the routing of the call as the lowest common supported bandwidth is only a 64 kbps content channel and a 56 kbps signaling channel.
Moreover, the overall cost of the call may be excessive as each company, owner, or service provider that controls each of the network elements may charge for routing the call through their particular network element. Local service providers or carriers are required to negotiate multiple complex network connection and access agreements with multiple other providers, and may reflect or pass along resulting increased costs to their subscribers.
In another scenario of the aforementioned example, suppose local service provider A provides voice over Internet protocol (VoIP) communication services to the calling subscriber. In addition to the cost and quality drawbacks previously discussed above for a POTS local carrier, additional undesired effects may occur for a VoIP local carrier. VoIP service providers generally use the public Internet to route calls. Each Internet node traversed by the call is typically not owned or controlled by a single provider, let alone the VoIP carrier itself, so the overall call path cannot be aggregately engineered to ensure call quality. The routing of VoIP calls across various nodes in the public Internet may result in delays and/or unreliable service. Public Internet access points may expose inherent security risks for VoIP calls. Moreover, VoIP originated calls to non-VoIP subscribers necessarily require conversion of the calls into standard telephony format for routing through the PSTN, thus incurring similar quality and cost issues as discussed above for a non-VoIP originated call.
Carriers or service providers have attempted to address these drawbacks by expanding the sizes of their networks and deploying higher-bandwidth network elements within their individual networks. With the current deregulated communication industry, however, a significant and sizeable percentage of communication calls are off-net, that is, the carrier or service provider controlling the network of the call's originating end is different from the carrier or service provider controlling the network of the call's terminating end. With multiple types of subscriber, local or other access technologies available to be used for communication calls (e.g., land-line, wireless, cable telephony, VoIP, POTS, etc.), off-net calls often require conversion to a different protocol or technology supported by the next network element. Multiple conversions along the call path may result in loss of data and therefore a decrease in call quality. The issues of call quality and cost may thus be traced, in a significant part, to the conversions between connections of different service provider networks in the call path.
Moreover, connections between different service provider networks add to the difficulty of feature transparency and/or availability to subscribers or end-users. Different networks operated by different carriers in the call path may not have sufficient bandwidth to support features and services available within an originating carrier's own network. A network provider may introduce new features within its network, but once a call goes off-net, the new features may not be compatible with the networks of other service providers. Each service provider is left to negotiate cost and technical interworking in a pair-wise fashion with any other service provider to whom it wishes to connect. Thus, feature and service transparency across multiple service providers may be difficult.